<div dir="ltr"><div>Announcement of the next gravity-theory webinar:</div><div><br></div><div><span style="font-variant-east-asian:normal;vertical-align:baseline;white-space:pre-wrap"><b>Katsuki Aoki</b><b> </b>(</span><span style="font-variant-east-asian:normal;vertical-align:baseline;white-space:pre-wrap">Yukawa Institute for Theoretical Physics, </span><span style="font-variant-east-asian:normal;vertical-align:baseline;white-space:pre-wrap">Kyoto University) </span><br></div><div><span style="font-variant-east-asian:normal;vertical-align:baseline;white-space:pre-wrap"><b>Monday, Jan 25th, h11:00am</b></span></div><div><span style="font-variant-east-asian:normal;vertical-align:baseline;white-space:pre-wrap"><br></span></div><div><span style="font-variant-east-asian:normal;vertical-align:baseline;white-space:pre-wrap"><div style="white-space:normal;line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-variant-east-asian:normal;vertical-align:baseline;white-space:pre-wrap">Title: <b>Non-linearly ghost-free higher curvature gravity</b></span></div><br></span></div><div><span style="white-space:pre-wrap">Abstract: </span><span style="white-space:pre-wrap">We find unitary and local theories of higher curvature gravity in the vielbein formalism, known as the Poincaré gauge theory by utilizing the equivalence to the ghost-free massive bigravity. We especially focus on three and four dimensions but extensions into a higher dimensional spacetime are straightforward. In three dimensions, a quadratic gravity L=R+T^2+R^2, where R is the curvature and T is the torsion with indices omitted, is shown to be equivalent to zwei-dreibein gravity and free from the ghost at fully non-linear orders. In a special limit, new massive gravity is recovered. When the model is applied to the AdS/CFT correspondence, unitarity both in the bulk theory and in the boundary theory implies that the torsion must not vanish. On the other hand, in four dimensions, the absence of ghost at non-linear orders requires an infinite number of higher curvature terms, and these terms can be given by a schematic form R/(1+R/alpha m^2)R where m is the mass of the massive spin-2 mode originating from the higher curvature terms and alpha is an additional parameter that determines the amplitude of the torsion. We also provide another four-dimensional ghost-free higher curvature theory that contains a massive spin-0 mode as well as the massive spin-2 mode.</span><br></div><div><span style="white-space:pre-wrap"><br></span></div><div><br></div><div><div>Zoom link: <a href="https://uniroma1.zoom.us/j/81283707469?pwd=SzkyMk5jRm0xcEN3WE5MYVh1RVFtQT09" target="_blank">https://uniroma1.zoom.us/j/81283707469?pwd=SzkyMk5jRm0xcEN3WE5MYVh1RVFtQT09</a> <br></div><div><div><div>ID meeting: 812 8370 7469<br>Passcode: 915450</div><div><br></div><div>List of the next gravity-theory webinars (calendar available here:<a href="https://calendar.google.com/calendar/u/1?cid=Y191MGo3bG9pYzE1bjBxdGFhN3A4MTlzNDg2Y0Bncm91cC5jYWxlbmRhci5nb29nbGUuY29t" target="_blank"> https://calendar.google.com/calendar/u/1?cid=Y191MGo3bG9pYzE1bjBxdGFhN3A4MTlzNDg2Y0Bncm91cC5jYWxlbmRhci5nb29nbGUuY29t</a>)</div><div><br></div><div>08/02/2021 h12:00 Jonas P. Pereira (Nicolaus Copernicus Astronomical Center, Warsaw PL): "Probing elastic quark phases in hybrid stars"<br>15/03/2021 h12:00 Danny Laghi & Gregorio Carullo (Pisa University, IT): "TBA"<br>24/03/2021 h16:00 William East (Perimeter Institute, CAN): "Black-hole mergers in Einstein-scalar-Gauss-Bonnet gravity"<br>14/04/2021 h16:00 Jorge Rocha (ISCTE, PT): "Recent developments toward the resolution of the information-loss paradox"<br></div><div><br></div><div>Cheers,<br></div></div><div>Paolo</div></div></div><div><br></div><div><div><br></div>-- <br><div dir="ltr" data-smartmail="gmail_signature"><div dir="ltr">Paolo Pani <br>Associate Professor<br>ERC StG Fellow, DarkGRA project<br>Junior Fellow, Scuola Superiore di Studi Avanzati Sapienza<br><br>Physics Department (Marconi Building), 3rd floor, room 334<br>Sapienza University of Rome<br>Piazzale Aldo Moro 5 - 00185 Rome (Italy) <br>+39 06 4991 4472 (int 24472)</div></div></div></div>
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